Adjusted RA costs push routers to conn limits

Description

We adjust costs based on proximity to conn limits but as RI publish interval is 37-50 minutes the cost info quickly becomes stale. In addition, we don't trigger a republish when cost changes. This leads to SSU being pushed to conn limit as we approach the next publish time.

We should either disregard cost when RI is old, or republish when cost changes, or both.

Additionally, cost values modifiers and router behavior in evaluating them for transport selection is poorly documented and should possibly be redesigned.

NetDB: Publish RI faster when costs change.
PLRIJ interval was 37-50 minutes. Reduce that by 4x,
but for 3 out of 4 times, only publish if something changes,
including cost. 4th time, always publish, as before.
This will hopefully reduce routers getting slammed to
conn limits on a transport.